REFRACTOR PROFESSIONAL OVERDRIVE
24
TROUBLESHOOTING INFORMATION
What happens if you finish building the kit and find that it doesn’t work right? Here are a few common
problems people have with this pedal and how to solve them.
The LED doesn’t light up.
First, does the pedal sound right? If you aren’t getting any sound, you probably have a power issue with
the whole circuit that is not specific to the LED, so you’ll want to look elsewhere for the problem.
If it does pass a signal, it’s probably just the LED itself. Is the flat side facing to the right (looking in the
enclosure from the back)? If it’s reversed, it won’t work. You’ll have to re-solder it the right way.
It works initially, but develops issues after about 30 seconds of being powered on.
Check that C16, the tantalum capacitor, is oriented correctly. Many people install this incorrectly due to
the fact that tantalums have the positive leg marked instead of the negative leg like electrolytics, so they
instinctively assume that the marking indicates negative.
All other issues
For any other problems, the first course of action is to measure the voltages on each pin of
the ICs using a digital multimeter. Set the multimeter to DC mode with a range of 20V or higher.
To start, touch the black lead to a ground point for the circuit. The easiest spot is inside a tapped screw
hole in one of the corners of the enclosure. This way the probe stays in place without needing to use
alligator clips. The circuit must of course be fully installed in the enclosure for this to work.
Then, touch the red probe to the first leg of IC1 and read the voltage. Note that IC pins are
labeled counter-clockwise from the upper-left, as shown in the diagram to the right.
These baseline voltages are taken using a 9.86V supply. Your measured voltages won’t be
exactly the same due to variance in power supplies and component tolerances. However,
if you see anything that’s more than around 0.5V higher or lower than these listed voltages, it’s a good
indicator of an issue and the voltages can help you or someone else narrow it down.
1
8
2
7
3
6
4
5
PIN
VOLTAGE
1
4.92V
2
4.92V
3
3V–4V (drifts)
4
0V
5
4.90V
6
4.92V
7
4.97V
8
9.86V
PIN
VOLTAGE
1
4.96V
2
4.92V
3
4.91V
4
-9.49V
5
4.91V
6
4.92V
7
4.87V
8
17.99V
PIN
VOLTAGE
1
9.86V
2
5.02V
3
0V
4
-4.66V
5
-9.49V
6
4.95V
7
6.35V
8
9.86V
IC1
IC2
IC3
